A Congestion Cost Allocation Method Considering P-Q Inter-action

The innovation of electric power industry from vertically integrated monopoly to competitive market creates a new developing opportunity for electric power industry, while gives rise to many new problems and challenges such as transmission congestion.Transmission congestion is a very important issue in power market. The limitation of transmission resources gives rise to power transmission bottleneck. It limits the free competition in power market. If we hope that the substance of market competition can be embodied, and to improve the efficiency of electric system as well as optimize resources, we must take efficient measures to manage transmission congestion. How to develop a logical method for congestion cost allocation becomes an important task.The paper formulizes most transmission congestion management methods presented recently. Typically, this cost is allocated using nodal price and uplift method. Nodal price results in merchandising surplus; uplift method fails to provide efficient price signal to customers and has the drawback of computational complexity although cost recovering. As a typical uplift method, power flow tracing method only considers the active power flow. In addition, because of the nonlinear character of electric power, the methods mentioned above are not absolutely fair in congestion cost allocation. Based on the new definition of usage for electrical components, the usage of bilateral transaction considering the P-Q inter-action is defined in this paper. The responsibility for electricity transmission congestion is allocated to the market members by accurate complex power flow tracing. The system congestion cost is allocated to relative lines first, and then to the market members according to its contribution to the system congestion. The proposed method eliminates the merchandising surplus, and counts the P-Q inter-action accurately by adopting active power loss in the definition of usage. Theoretical analysis and simulation study of two example systems show that the allocation of congestion cost by this method is fair and accord with the fact of the power system. In addition, this method provides accurate and economical signals to customers.